What size snatchblocks for front winch?

[rmgill]

On the Deuce, what are the best sized snatchblocks for single and double line pulls using the front winch?

 

[red devils dude]

I'd go 30,000lb.

 

[rizzo]

the snatch block for a M543A2 is a 8 inch single sheave, 5/8 rope, 10ton working load.
I don't understand how they can use that on a winch rated for 10ton. Wouldn't they need a block that rates at 20ton? twice what the winch will do. 20ton is whats gonna be on the block hook. and 10 ton on each line. Anyone know??? Same with the rear winch. They have a block that weighs @80lbs but only rated at 15ton. the winch is 22.5 ton.

Ryan. If you find a block at a good price let me know. I would be interested in getting one too.

 

[rmgill]

So far the only ones that I've found that aren't $400 or more are these warn numbers:
http://www.roughgear.com/warn/snatchblocks2.html

Seems like they'd work pretty well to with the anchor point going into a celvis on the truck's bumper.

Oh, according to this calculator (http://catalog.thecrosbygroup.com/Calculators/Calculators/snatchblockrigcalc.htm), if you run the pulled line back to the pulling truck you're only looking at the load of the pulled object being the load on the block. I suspect that if you ran your line from winch to block on load to block on truck to load, that you'd be looking at double the line pull on the block on the load.

 

[cranetruck]

Aren't snatch blocks rated/used according to the size of wire rope that can be properly fitted on the sheave? In other words, use the snatch block that fits your size wire rope.

 

[cranetruck]

This is from the TM 5-725 "Rigging":

 

[rizzo]

Aren't snatch blocks rated/used according to the size of wire rope that can be properly fitted on the sheave? In other words, use the snatch block that fits your size wire rope.

the smaller snatch blocks sometimes talk about various sizes all the bigger ones seem to have one size. I like that warn block, but it says 7/16 cable. isn't the M35 winch 1/2 cable?

 

[rizzo]

if you run the pulled line back to the pulling truck you're only looking at the load of the pulled object being the load on the block. I suspect that if you ran your line from winch to block on load to block on truck to load, that you'd be looking at double the line pull on the block on the load.

this is right. so if you have a 13000lb truck and it is stuck bad it could need 39,000lb of pull to get it out. I think the military says figure a 3:1 ratio on rolling vehicle weight to stuck vehicle weight. This isn't the case all the time, but it is a rule of thumb. I think the winches are meant to be used in conjunction with the wheels driving as an assist tool.

lets say you were stuck in the middle range and needed 26,000lbs of force to get out. then that would have to be the load rating on the block. 26000lbs WLL

None of this explains why the Military blocks for the wreckers are only rated at what the winch is rated at. It would make the job for the winch and cable easier but you would still have a 20,000 limit (for the front winch)

 

[mangus580]

This is the one I got I I think its the one that came with the deuce.

http://www.galleria-e.com/cgi-bin/Colemans.storefront/en/product/190601

 

[ida34]

the snatch block for a M543A2 is a 8 inch single sheave, 5/8 rope, 10ton working load.
I don't understand how they can use that on a winch rated for 10ton. Wouldn't they need a block that rates at 20ton? twice what the winch will do. 20ton is whats gonna be on the block hook. and 10 ton on each line. Anyone know??? Same with the rear winch. They have a block that weighs @80lbs but only rated at 15ton. the winch is 22.5 ton.

Ryan. If you find a block at a good price let me know. I would be interested in getting one too.

The deuce winch is rated at 10,000 lbs not 10 tons. It's ton rating is 5 tons and I think the snatch block for the deuce front winch is 10 ton or 20,000 lbs. That means the 10 ton snatch block is just right. math is tough

 

[Rattlehead]

According to that chart, a winch using 1/2" diameter cable in a 6x19 thread, would require a 17" diameter sheave?

 

[rizzo]

the snatch block for a M543A2 is a 8 inch single sheave, 5/8 rope, 10ton working load.
I don't understand how they can use that on a winch rated for 10ton. Wouldn't they need a block that rates at 20ton? twice what the winch will do. 20ton is whats gonna be on the block hook. and 10 ton on each line. Anyone know??? Same with the rear winch. They have a block that weighs @80lbs but only rated at 15ton. the winch is 22.5 ton.

Ryan. If you find a block at a good price let me know. I would be interested in getting one too.

The deuce winch is rated at 10,000 lbs not 10 tons. It's ton rating is 5 tons and I think the snatch block for the deuce front winch is 10 ton or 20,000 lbs. That means the 10 ton snatch block is just right. math is tough

the M543A2 is not a deuce.

 

[rizzo]

This is the one I got I I think its the one that came with the deuce.

http://www.galleria-e.com/cgi-bin/Colemans.storefront/en/product/190601

I think that is a great price too. Only 5 ton though????

 

[cranetruck]

Here are two of those Coleman snatch blocks in use. Barely visible, one on the pipeline truck bed and one out of view on Kenny's M275. Pulling the deuce tractor rear sideways was no problem with this "K-boom" winch set-up.

 

[rizzo]

more cool pics by cranetruck

 

[rmgill]

So do we have any consensus for what a snatch block needs to be rated at for safe recovery work of a deuce or similar with the 10,000 lb winch? Clearly the shear pin is going to limit the load on the winch cable and PTO system, but what about the block themselves.

 

[Elwenil]

Also you need to remember that while the drum is only carrying half the load, the cable gets it all as well as any mounting point that the snatch block is hooked to. There are several good books on recovery as well as a few military manuals that can help you out and keep you out of trouble.

 

[rmgill]

actually, isn't the cable at a lower rating as well along each strand? The mounting point for the block is going to depend on the rigging as well I think. Rig back to a block and sure, it'll be double. Rig to the clevis of your truck and it'll be lower forces.


Hmm, would the cable along each lay have the total pull or not....

 

[rmgill]

Ah, TM 5-725 is online
http://72.14.203.104/search?q=cache...+5-725&hl=en&gl=us&ct=clnk&cd=1&client=safari

Broken up by chapter.

Seems like I have this TM at home too. Need to dig it up.

 

[rizzo]

Also you need to remember that while the drum is only carrying half the load, the cable gets it all as well as any mounting point that the snatch block is hooked to. There are several good books on recovery as well as a few military manuals that can help you out and keep you out of trouble.

are you talking about the winch drum? the cable and the winch only get half or whatever the winch pull is. On a 10k winch each cable leg(one going too the block and one coming from the block) get 10k. When you hook the cable coming back from the block to your truck or another anchor point that has to withstand the 10k that is on the cable.
on the other side of the snatch block you have 20k of pressure. whatever you hook the block too has to withstand 20k. on another MV I would hook two straps to each shackle and then to the block. each one of the straps have to withstand 10k each. They share the 20k load from the block. each shackle will have 10k on it instead of 20k(if you just used one shackle). Keep in mind that using a sling setup your load ratings on the straps would be reduced depending on what angle the sling is at. Since most MV's have the shackles reletily close together I don't think that this is a big factor (I use 2 11ft straps with a rating of 45k each).